1. Field of the Invention
The present invention relates to a ball detecting apparatus which can surely detect balls, for example, ball-shaped semiconductor devices provided with integrated function elements, when the balls are carried one by one in a transparent tube using transparent liquid as a carrier, for example, in the process of manufacturing the ball-shaped semiconductor devices.
2. Description of the Prior Art
These days, a ball semiconductor device is attracting attention. The ball semiconductor device is a ball-shaped semiconductor device of 1 mm or so in diameter provided with monolithicly integrated function elements such as a transistor and the like. It has been also proposed to construct a semiconductor circuit/system having a predetermined circuit function by combining a plurality of kinds of ball semiconductor devices each having a function of a basic element such as a sensor or a memory.
In the process of manufacturing ball semiconductor devices of that kind, balls that are ball semiconductor devices are carried one by one using transparent liquid like water as a carrier, in a ball carrying passage formed, for example, out of a transparent tube. Here, in controlling the manufacturing process, it is important to count the number of balls that have been carried, for example, in the tube. Conventionally, with a photo sensor that comprises a light source and a photo detector arranged opposite to each other with the tube between and has an optical path crossing the tube, balls passing the optical path are detected, making use of the fact that balls carried in the tube intercept the light.
However, sometimes, bubbles are produced in the transparent liquid as a carrier, and cause errors in detecting the balls.
Specifically, as schematically shown in FIG. 7, in a conventional ball detecting apparatus, an optical fiber 3 for projection is arranged on one side of the transparent tube 1 that forms a ball carrying passage to guide the light emitted from the light source 2 and project it to the transparent tube 1. Further, an optical fiber 4 for reception is arranged on the opposite side of the transparent tube 1 to guide the light having crossed the tube 1 to the photo detector 5. As shown in FIG. 8, when a ball 7 carried in the tube 1 by the transparent liquid 6 as a carrier intercepts the light crossing the tube 1, the photo detector 5 ceases to receive light. By making use of this, the ball 1 is detected.
However, sometimes, bubbles 8 are produced in the transparent liquid 6. The bubbles 8 can act as concave lenses. Therefore, sometimes, the light projected to the tube 1 is deflected as shown in FIG. 9 and cannot reach the optical fiber 4 for reception. As a result, the photo detector 5 ceases to receive the light from the light source 2, and the bubbles 8 are mistakenly detected as a ball 7. This may put the control of manufacturing process out of order. Thus, various conventional attempts are all devoted to preventing bubbles 8 being produced in the transparent liquid.
An object of the present invention is to provide a highly practical ball detecting apparatus having a simple structure and being capable of surely detecting balls carried in a tube without being affected by bubbles produced in transparent liquid.
The present invention provides technique for surely detecting non-transparent balls carried one by one in a transparent tube as a ball carrying passage using transparent liquid as a carrier, optically with an optical sensor comprising a light source and a photo detector.
The ball detecting apparatus of the present invention especially uses, as the light source of the optical sensor, a surface light source that projects diffused light having a predetermined beam cross section and a predetermined beam spread angle, from a side of the tube into the tube. The photo detector is arranged such that a light receiving area of the photo detector is opposite to the surface light source with the tube between. The photo detector receives a component of the diffused light that has passed through the transparent liquid toward the light receiving area, and/or a component of the diffused light that has been deflected by a bubble produced in the transparent liquid and come out of the transparent liquid toward the light receiving area. The light receiving area is adapted to be able to be completely shielded from the diffused light by the balls carried in the tube. Judging means is provided to judge the presence of the balls carried in the tube from the level of a light receiving signal sent from the photo detector.
Specifically, the ball detecting apparatus according to the present invention uses diffused light having a predetermined beam cross section and a predetermined beam spread angle as light for use in detecting balls, and uses a photo detector whose light receiving area is of dimensions such that it can be completely shielded from the diffused light by the balls carried in the tube, momentarily. Thus, the photo detector detects a component of the diffused light that has passed through the transparent liquid directly toward the light receiving area, and/or a component of the diffused light that has been deflected by a bubble produced in the transparent liquid to travel indirectly toward the light receiving area.
In a desirable embodiment of the present invention, the photo detector has a predetermined angular aperture, and a field of view determined by the angular aperture and the light receiving area is optically located such that the light receiving area can be completely shielded from the diffused light by the balls.
In a desirable embodiment of the present invention, the surface light source is arranged opposite to one side of the tube with an optical fiber between, and the photo detector is arranged opposite to the opposite side of the tube with an optical fiber between. The surface light source may include a light diffusing plate to produce the diffused light.
The balls may be, for example, ball-shaped semiconductor devices provided with or to be provided with an integrated circuit of function elements. Thus, the ball detecting apparatus according to the present invention is suitable to be used in the process of manufacturing such ball-shaped semiconductor devices.
With the ball detecting apparatus according to the present invention, in optically detecting balls carried in a tube using transparent liquid as a carrier, balls can be surely detected excluding the influence of bubbles in the transparent liquid easily and surely. Thus, the number of balls carried in the tube can be counted correctly, which, for example, makes the control of process of manufacturing ball semiconductor devices reliable and sure. In addition, the ball detecting apparatus according to the present invention has a simple structure, therefore it has a great practical effect such that the ball detecting apparatus operating with high reliability can be manufactured at low costs.